FIELD OF THE INVENTION
[0001] The present invention relates to coating compositions that are useful for coating
containers of various sorts such as food and beverage containers. The compositions
are particularly useful for coating the interior of the containers.
BACKGROUND OF THE INVENTION
[0002] Coatings are typically applied to the interior of metal food and beverage containers
to prevent the contents from contacting the metal surface of the container. Contact
with certain foods, particularly acidic products, can cause the metal container to
corrode. This corrosion results in contamination and deterioration in the appearance
and taste of the food or beverage product.
[0003] Many of the coating compositions for food and beverage containers are based on epoxy
resins that are the polyglycidyl ethers of bisphenol A. Bisphenol A in packaging coatings
can be either bisphenol A itself (BPA) or derivatives thereof, such as diglycidyl
ethers of bisphenol A (BADGE) and epoxy novolak resins. These coatings have excellent
flexibility and adhesion to metal substrates. However, bisphenol A and derivatives
thereof are problematic. Although the balance of scientific evidence available to
date indicates that small trace amounts of BPA or BADGE that might be released from
existing coatings does not pose health risks to humans. These compounds are nevertheless
perceived by some as being harmful to human health. Consequently, there is a strong
desire to eliminate these compounds from coatings for food and beverage containers.
[0004] Replacement coating compositions are typically based on hydroxyl group-containing
polymers and aminoplast or phenolplast curing agents. Although these coatings have
good adhesion, they lack the flexibility required to prevent corrosion that occurs
when the coating undergoes microcracking due to severe deformation of the metal. In
2-piece food cans, for example, microcracking occurs in the headspace due to the double-seam
process that affixes the can end after filling. This is commonly known as "pressure
ridge" cracking. Corrosive foodstuffs infiltrate the coating through the microcracks
and corrode the metal surface causing corrosion, delamination of the coating and eventual
perforation of the can which spoils the food. Because of the susceptibility of acrylic-based
coatings to pressure-ridge cracking, they are currently inferior to industry standard
BPA-containing coatings in the packaging coatings industry because they cannot hold
strongly corrosive foodstuffs.
[0005] Also, the replacement coating compositions provide coatings with poor slip properties.
This poses a problem with solid foods such as canned meats. When the can is opened,
the meat does not release from the interior of the can and must be manually scooped
out of the can.
SUMMARY OF THE INVENTION
[0007] The present invention provides a composition as defined in claim 1.
[0008] The present invention also provides a coated article comprising:
- (a) a substrate, and
- (b) a coating deposited on at least a portion of the substrate from the composition
described above.
[0009] The polysilicone resin increases the flexibility of the resultant coating without
adversely affecting adhesion. Phenylated polysilicone resins have excellent compatibility
with the organic components of the coating composition. Moreover, incorporation of
the polysilicone resin in the coating composition reduces the surface tension of the
coating significantly which repels water and improves surface slip offering several
additional novel uses for food packaging such as meat release. Coatings for canned
meats must have high surface slip allowing meat-based foodstuffs to easily be removed
from the can. Additionally, the polarity of the phenylated polysilicone resins allows
them to be used in water-based formulations yielding stable dispersions.
DETAILED DESCRIPTION
[0010] As used herein, unless otherwise expressly specified, all numbers such as those expressing
values, ranges, amounts or percentages may be read as if prefaced by the word "about",
even if the term does not expressly appear. Moreover, it should be noted that plural
terms and/or phrases encompass their singular equivalents and vice versa. For example,
"a" polymer, "a" crosslinker, and any other component refers to one or more of these
components.
[0011] Also, although the resinous binder, including film formers, crosslinkers and the
polysilicone resin are all resinous materials, it is intended that they are all different
from one another.
[0012] When referring to any numerical range of values, such ranges are understood to include
each and every number and/or fraction between the stated range minimum and maximum.
[0013] As employed herein, the term "polyol" or variations thereof refers broadly to a material
having an average of two or more hydroxyl groups per molecule. The term "polycarboxylic
acid" refers to the acids and functional derivatives thereof, including anhydride
derivatives where they exist, and lower alkyl esters having 1-4 carbon atoms.
[0014] As used herein, the term "polymer" refers broadly to prepolymers, oligomers and both
homopolymers and copolymers. The term "resin" is used interchangeably with "polymer".
[0015] The terms "acrylic" and "acrylate" are used interchangeably (unless to do so would
alter the intended meaning) and include acrylic acids, anhydrides, and derivatives
thereof, such as their C
1-C
5 alkyl esters, lower alkyl-substituted acrylic acids, C
1-C
2 substituted acrylic acids, such as methacrylic acid, ethacrylic acid, and their C
1-C
5 alkyl esters, unless clearly indicated otherwise. These monomers can be polymerized
by themselves or with vinyl monomers such as vinyl aromatic monomers and allylic monomers.
The terms "(meth)acrylic" or "(meth)acrylate" are intended to cover both the acrylic/acrylate
and methacrylic/methacrylate forms of the indicated material, e.g., a (meth)acrylate
monomer. The term "acrylic polymer" refers to polymers prepared from one or more acrylic
monomers.
[0016] As used herein, "a" and "the at least one" and "one or more" are used interchangeably.
Thus, for example, a coating composition that comprises "a" polymer can be interpreted
to mean the coating composition includes "one or more" polymers.
[0017] As used herein, the molecular weights are determined by gel permeation chromatography
using a polystyrene standard. Unless otherwise indicated, molecular weights are on
a weight average basis (M
w).
[0018] The resinous vehicle typically consists of a resinous film former and a curing or
crosslinking agent. The resinous film-forming material can be an acrylic polymer.
The acrylic polymer is preferably a polymer derived from one or more acrylic monomers
and other copolymerizable vinyl monomers. Furthermore, blends of acrylic polymers
can be used. Preferred monomers are acrylic acid, methyl acrylate, ethyl acrylate,
propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, methacrylic acid,
methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate,
pentyl methacrylate and hexyl methacrylate. The acrylic polymer may also contain hydroxyl
groups which typically are derived from hydroxy-substituted acrylic or methacrylic
acid esters. Examples include hydroxyethyl acrylate and hydroxypropyl methacrylate.
[0019] Examples of vinyl monomers are vinyl esters including vinyl acetate, vinyl propionate,
vinyl butyrates, vinyl benzoates, vinyl isopropyl acetates, and similar vinyl esters.
Vinyl halides include vinyl chloride, vinyl fluoride, and vinylidene chloride. Vinyl
aromatic hydrocarbons include styrene, methyl styrenes, and similar lower alkyl styrenes,
chlorostyrene, vinyl toluene, vinyl naphthalene, divinyl benzoate, and cyclohexene.
Vinyl aliphatic hydrocarbon monomers include alpha olefins such as ethylene, propylene,
isobutylene, and cyclohexyl as well as conjugated dienes such as butadiene, methyl-2-butadiene,
1,3-piperylene, 2,3-dimethyl butadiene, isoprene, cyclopentadiene, and dicyclopentadiene.
Vinyl alkyl ethers include methyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl
ether, and isobutyl vinyl ether. Examples of allylic monomers include allyl alcohol
and allyl chloride.
[0020] The acrylic polymer typically is prepared by conventional solution polymerization
techniques using free radical initiators such as azo or peroxide catalyst.
[0021] The molecular weight (M
w) of the acrylic polymer component is preferably at least 5,000 gram/mole, more preferably
from 15,000 to 100,000 gram/mole. The acrylic polymer typically has an acid value
of 30 to 70, such as 40 to 60 mg KOH/g; a hydroxyl value of 20 to 100, such as 30
to 70 mg of KOH/g
[0022] Typically curing agents are present in the resinous vehicle, which are reactive with
the acrylic polymers. Suitable curing agents are phenolplasts or phenol-formaldehyde
resins and aminoplast or triazine-formaldehyde resins. The phenol-formaldehyde resins
are preferably of the resol type. Examples of suitable phenols are phenol itself,
butyl phenol, xylenol and cresol. Cresol-formaldehyde resins, typically etherified
with butanol, are often used. For the chemistry in preparation of phenolic resins,
reference is made to "
The Chemistry and Application of Phenolic Resins or Phenolplasts", Vol. V, Part I,
edited by Dr. Oldring; John Wiley & Sons/Cita Technology Limited, London, 1997. Examples of commercially available phenolic resins are PHENODUR
® PR285 and BR612 and those resins sold under the trademark BAKELITE
®, typically BAKELITE 6581 LB.
[0023] Examples of aminoplast resins are those which are formed by reacting a triazine such
as melamine or benzoguanamine with formaldehyde. Preferably, these condensates are
etherified typically with methanol, ethanol, butanol including mixtures thereof. For
the chemistry preparation and use of aminoplast resins, see "
The Chemistry and Applications of Amino Crosslinking Agents or Aminoplast", Vol. V,
Part II, page 21 ff., edited by Dr. Oldring; John Wiley & Sons/Cita Technology Limited,
London, 1998. These resins are commercially available under the trademark MAPRENAL
® such as MAPRENAL MF980 and under the trademark CYMEL
® such as CYMEL 303 and CYMEL 1128, available from Cytec Industries.
[0024] The silicone resins that are used in the practice of the invention are functional
silicone resins, that is, they contain functional groups that are reactive with functional
groups associated with the resinous binder. Typically, these groups are active hydrogen
groups that are reactive with cofunctional groups associated with the curing or crosslinking
agent of the resinous binder such as aminoplast or phenolplast. Also, the silicone
resins can be phenylated silicone resins containing a C
6H
5-S≡ bond. The phenyl group is beneficial in that it compatibilizes the silicone resin
with the other resinous ingredients in the coating composition in that all of the
resinous ingredients can be uniformly dissolved or dispersed in a diluent, that is,
the silicone resin will not form a separate phase from the other resinous ingredients
in the coating composition.
[0025] The phenylated silicone resin used in the composition according to the invention
is advantageously an alkyl-phenyl silsesquioxane resin.
[0026] This resin advantageously comprises units of the following formulae:
(R'SiO3/2)x and (C6H5SiO3/2)y
R' is selected from the group consisting of a linear or branched alkyl group comprising
from 1 to 20 carbon atoms, such as from 2 to 8 carbon atoms, a cycloalkyl group comprising
from 5 to 20 carbon atoms, such as from 6 to 12 carbon atoms, and a hydroxyl group,
and
x and y independently ranging from 0.05 to 0.95, such that x is 0.1 to 0.3 and y is
0.7 to 0.9, and x+y = 1.
[0027] x and y representing the mole fraction of the siloxane units (R'SiO
3/2)
x and (C
6H
5SiO
3/2)
y with respect to the total number of moles of siloxane units in the phenylated silicone
resin.
[0028] Usually R' is a mixed alkyl group and hydroxyl group such that the silicone resin
has a hydroxyl content of 3 to 20, such as 5 to 10 percent by weight based on solid
weight of the silicone resin.
[0029] The phenylated silicone resin advantageously comprises at least 20 mole percent,
preferably at least 30 mole percent, better still at 40 mole percent, even better
still at least 50 mole percent and better still at least 60 mole percent of siloxane
units (R'SiO
3/2)
x and (C
6H
5SiO
3/2)
y, with respect to the total number of siloxane units present in the phenylated silicone
resin.
[0030] According to one embodiment, the content of siloxane units (R'SiO
3/2)
x and (C
6H
5SiO
3/2)
y, can range up to 100 mole percent, with respect to the total number of siloxane units
present in the phenylated silicone resin.
[0031] Examples of alkyl groups are methyl, ethyl and propyl; examples of cycloalkyl groups
are cyclohexyl.
[0032] The alkyl-phenyl silsesquioxane resins can contain additional siloxy units such as
(i) (R
13SiO
1/2)
a, (ii) (R
22SiO
2/2)
b, (iii) (R
3SiO
3/2)
c, or (iv) (SiO
4/2)
d units. The amount of each unit present in the alkyl-phenyl silsesquioxane resin can
be expressed as a mole fraction of the total number of moles of all siloxy units present
in the alkyl-phenyl silsesquioxane resin. Thus, the alkyl-phenyl silsesquioxane resins
of the present invention comprise the units:
- (i) (R13SiO1/2)a
- (ii) (R22SiO2/2)b
- (iii) (R3SiO3/2)c
- (iv) (SiO4/2)d
- (v) (R'SiO3/2)x and
- (vi) (C6H5SiO3/2)y
wherein
R' is defined above,
R1, R2 and R3 are independently an alkyl group having from 1 to 8 carbon atoms such as methyl,
ethyl and propyl; an aryl group such as phenyl and tolyl, a hydroxyl group, a carbinol
group or an amino group,
a, b, c and d have a value of zero to 0.4,
x and y have a value of 0.05 to 0.95, such as x having a value of 0.1 to 0.3 and y
having a value of 0.7 to 0.9,
with the provisos that the value of x+y is equal to or greater than 0.60, and the
value of a+b+c+d+x+y = 1.
[0033] Typically, the acrylic polymer and/or the polyester polymer is used in amounts of
40 to 85, such as 30 to 70 percent by weight; the crosslinking agent is present in
amounts of 5 to 50, such as 15 to 40 percent by weight and the polysilicone resin
is present in amounts of 10 to 30, such as 15 to 20 percent by weight; the percentages
by weight being based on the weight of total resin solids in the coating composition.
[0034] Optional ingredients can be included in the coating composition. Typically, the coating
composition will contain a diluent, such as water, or an organic solvent or a mixture
of water and organic solvent to dissolve or disperse the ingredients of the composition.
The organic solvent is selected to have sufficient volatility to evaporate essentially
entirely from the coating composition during the curing process such as during heating
from 175-205°C. for about 5 to 15 minutes. Examples of suitable organic solvents are
aliphatic hydrocarbons such as mineral spirits and high flash point VM&P naphtha;
aromatic hydrocarbons such as benzene, toluene, xylene and solvent naphtha 100, 150,
and 200; alcohols, for example, ethanol, n-propanol, isopropanol, and n-butanol; ketones
such as acetone, cyclohexanone and methylisobutyl ketone; esters such as ethyl acetate,
and butyl acetate; glycols such as butyl glycol, glycol ethers such as methoxypropanol,
ethylene glycol monomethyl ether and ethylene glycol monobutyl ether. Mixtures of
various organic solvents can also be used. For aqueous compositions, the resinous
vehicle typically has acid groups, such as acid functional acrylic polymers, that
are at least partially neutralized with an amine to assist in the dispersion or dissolution
of the resinous vehicle in the aqueous medium. When present, the diluent is used in
the coating compositions in amounts of 20 to 80, such as 30 to 70 percent by weight
based on total weight of the coating composition.
[0035] Adjuvant resins such as polyester polyols, polyether polyols and polyurethane polyols
may be included in the coating compositions to maximize certain properties of the
resultant coating. When present, the adjuvant resin is used in amounts of up to 50,
typically 2-50 percent by weight based on weight of resin solids of the coating composition.
[0036] Another optional ingredient that is typically present in the coating composition
is a catalyst to increase the rate of cure or crosslinking of the coating compositions.
Generally acid catalyst may be used and is typically present in amounts of 0.05 to
5 percent by weight. Examples of suitable catalyst are dodecyl benzene sulfonic acid,
methane sulfonic acid, paratoluene sulfonic acid, dinonyl naphthalene disulfonic acid
and phenyl phosphonic acid.
[0037] Another useful optional ingredient is a lubricant, for example, a wax which facilitates
manufacture of metal closures by imparting lubricity to the sheets of the coated metal
substrate. Preferred lubricants include, for example, carnauba wax and polyethylene-type
lubricants. If used, the lubricant is preferably present in the coating compositions
of at least 0.1 percent by weight based on weight of resin solids in the coating composition.
[0038] Another useful optional ingredient is a pigment such as titanium dioxide. If used,
the pigment is present in the coating compositions in amounts no greater than 70 percent
by weight, preferably no greater than 40 percent by weight based on total weight of
solids in the coating composition.
[0039] Surfactants can optionally be added to the coating composition to aid in flow and
wetting of the substrate. Examples of suitable surfactants include, nonyl phenol polyether
and salts. If used, the surfactant is present in amounts of at least 0.01 percent
and no greater than 10 percent based on weight of resin solids in the coating composition.
[0040] In certain embodiments, the compositions used in the practice of the invention are
substantially free, may be essentially free and may be completely free of bisphenol
A and derivatives or residues thereof, including bisphenol A ("BPA") and bisphenol
A diglycidyl ether ("BADGE"). Such compositions are sometimes referred to as "BPA
non intent" because BPA, including derivatives or residues thereof, are not intentionally
added but may be present in trace amounts because of unavoidable contamination from
the environment. The compositions are substantially free and may be essentially free
and may be completely free of bisphenol F and derivatives or residues thereof, including
bisphenol F and bisphenol F diglycidyl ether ("BPFG"). The term "substantially free"
as used in this context means the compositions contain less than 1000 parts per million
(ppm), "essentially free" means less than 100 ppm and "completely free" means less
than 20 parts per billion (ppb) of any of the above-mentioned compounds, derivatives
or residues thereof.
[0041] The compositions of the present invention can be prepared according to methods well
known in the art. For example, using an acid functional acrylic polymer as the resinous
vehicle, the polymer is neutralized with an amine to between 20-80 percent of the
total theoretical neutralization. The neutralized acrylic polymer is then dispersed
in water followed by the addition of polysilicone resin. The mixture is then thinned
with more water to achieve a manageable viscosity. Crosslinkers and additives are
then added followed by thinning with additional water to achieve the desired solids
and viscosity.
[0042] As mentioned above, the coating compositions of the present invention can be applied
to containers of all sorts and are particularly well adapted for use on food and beverage
cans (e.g., two-piece cans, three-piece cans, etc.).
[0043] The compositions can be applied to the food or beverage container by any means known
in the art such as roll coating, spraying and electrocoating. It will be appreciated
that for two-piece food cans, the coating will typically be sprayed after the can
is made. For three-piece food cans, a flat sheet will typically be roll coated with
one or more of the present compositions first and then the can will be formed. As
noted above, the percent solids of the composition can be adjusted based upon the
means of application. The coating can be applied to a dry film weight of 24 mgs/26
cm
2 (4 in
2) to 12 mgs/26 cm
2 (4 in
2), such as 20 mgs/26 cm
2 (4 in
2) to 14 mgs/26 cm
2 (4 in
2).
[0044] After application, the coating is then cured. Cure is effected by methods standard
in the art. For coil coating, this is typically a short dwell time (i.e., 9 seconds
to 2 minutes) at high heat (i.e., 485°F. (252°C.) peak metal temperature); coated
metal sheets typically cure longer (i.e., 10 minutes) but at lower temperatures (i.e.,
400°F. (204°C.) peak metal temperature). For spray applied coatings on two-piece cans,
the cure can be from 5 to 8 minutes, with a 90-second bake at a peak metal temperature
of 415°F. (213°C.) to 425°F. (218°C.).
[0045] Any material used for the formation of food cans can be treated according to the
present methods. Particularly suitable substrates include tin-plated steel, tin-free
steel and black-plated steel.
[0046] The coatings of the present invention can be applied directly to the steel, without
any pretreatment or adhesive aid being added to the metal first. In addition, no coatings
need to be applied over top of the coatings used in the present methods.
[0047] The compositions of the present invention perform as desired both in the areas of
adhesion and flexibility.
EXAMPLES
[0048] The following examples are offered to aid in understanding of the present invention.
Unless otherwise indicated, all parts and percentages are by weight.
Example 1
[0049] A coating composition was prepared from the following ingredients:
| Ingredients |
Parts by Weight |
Percent by Weight Based on Total Coating Composition Weight |
Percent by Weight Based on Weight of Resin Solids |
| Cowles Grind |
|
|
|
| Acrylic Resin 50% resin solids in butanol1 |
670 |
14.0 |
33.7 |
| Dimethylethanolamine |
38.9 |
0.8 |
|
| PR 516 Phenolic 50% resin solids in butanol2 |
899 |
18.8 |
43.4 |
| TiO2 |
349 |
7.3 |
|
| Epikure 3100 80% resin solids in isopropanol3 |
58.5 |
1.2 |
4.5 |
| Deionized water |
728 |
15.2 |
|
| |
|
|
|
| Let Down in Thin Tank |
|
|
|
| PR 516 Phenolic |
170 |
3.6 |
8.2 |
| 50% Resin solids in butanol |
|
|
|
| Butanol |
38 |
0.8 |
|
| 2-butoxy ethanol |
98 |
2.0 |
|
| Channel Black Dispersion |
52 |
1.1 |
|
| Oleic acid |
9 |
0.2 |
|
| Caprilic acid |
9 |
0.2 |
|
| Polysilicone Resin |
150 |
3.1 |
10.1 |
| 70% Resin solids in butanol4 |
|
|
|
| Surfynol 1045 |
|
|
|
| Deionized water |
1500 |
31.3 |
|
| |
4802 |
100.3 |
100 |
1 Acrylic Resin was prepared using conventional solution polymerization techniques
using a peroxide catalyst. The resin had a methacrylic acid/styrene/butyl acrylate/ethyl
acrylate weight ratio of 25/30/20/25 and an Mw of 20,000 to 50,000.
2 Cresol phenolic available from Cytec Industries.
3 Amine terminated polyamide from Momentive.
4 Xiameter RSN217 from Dow Corning.
5 Acetylenic diol from Air Products. |
[0050] The Cowls Grind paste is prepared by combining the constituents listed in the order
of addition shown using a commercial Cowls mixer set to high speed. Grind to no higher
than100°F (38° C) or until Fineness of Grind gauge indicates grind less than 6.5 µm
(microns). Withhold deionized water until fineness of grind is achieved and paste
is ready for let-down. Once deionized water has been added to grind paste, pump grind
paste into thin-down tank. Begin mixing at high speed; add let-down constituents in
order shown. Adjust finished coating to desired viscosity with deionized water.
Example 2 (Comparative)
[0051] A coating composition similar to Example 1 was prepared but omitting the polysilicone
resin.
Example 3 (Comparative)
[0052] A coating composition similar to Example 1 was prepared but substituting a polyethylene
wax for the polysilicone resin. The composition was prepared from the following ingredients:
| Ingredients |
Parts by Weight |
Percent by Weight Based on Weight of Resin Solids |
| Cowles Grind |
|
|
| Acrylic Resin of Ex. 1 |
709 |
31.5 |
| Dimethylethanolamine |
83 |
|
| TiO2 |
574 |
|
| Epikure 3100 of Ex. 1 |
71 |
4.8 |
| Deionized Water |
777 |
|
| |
|
|
| Let Down in Thin Tank |
|
|
| PR 516 of Ex. 1 |
1140 |
60.2 |
| 2-butoxyethanol |
130 |
|
| Butanol |
210 |
|
| Mineral Spirits |
57 |
|
| Channel Black Dispersion |
53 |
|
| |
|
|
| Polyethylene Dispersion1 |
165 |
3.5 |
| Surfynol 104 |
98 |
|
| Deionized Water |
1700 |
|
| Deionized Water |
250 |
|
| |
6051 |
100 |
[0053] The Cowls Grind paste is prepared as Example 1 by combining the constituents listed
in the order of addition shown using a commercial Cowls mixer set to high speed. Grind
to no higher than 100°F (38°C) or until Fineness of Grind gauge indicates grind less
than 6.5 µm (microns). Withhold deionized water until fineness of grind is achieved
and paste is ready for let-down. Once deionized water has been added to grind paste,
pump grind paste into thin-down tank. Begin mixing at high speed; add let-down constituents,
including Michelman ML103DIF lubricant additive in order shown. Adjust finished coating
to desired viscosity with deionized water.
[0054] Examples 1-3 were spray applied to the interior of 211 x 400 electro tin plated steel
D&I cans at a film weight of 220 mg, +/- 10 mg; and/or can ends at a coating weight
of 16 - 18 mg/26 cm
2 (4 in
2). The spray applied coating is cured by heating the D&I can in a four zone IBO oven
to achieve 400°F (204°C) on the dome (e.g., bottom of can) for 90 seconds for 5 minutes
total bake. The roll applied coating is cured by heating the coated steel sheet for
12 minutes at 400°F (204°C). The coil applied coating is cured for 18 seconds with
a PMT of 500°F (260°C) for 3 to 5 seconds. The can ends were seamed onto the cans
containing a meat based ground beef composition that simulates dog food. The cans
were filled to ½" headspace and were steam processed for 90 minutes at 121°C and evaluated
for microcracking in the headspace by testing metal exposure and visible corrosion.
The results are reported below:
| Examples |
Evaluation |
| 1 |
No microcracking |
| 2 |
Severe microcracking |
| 3 |
Severe microcracking |
[0055] The coatings of Examples 1-3 were also evaluated for slip or meat release properties.
The test that was used was to fill the steel cans coated as described above with the
coating compositions of Examples 1-3 with a ground beef composition that simulated
dog food. The composition is made from equal parts by volume of ground beef (30 percent
fat), Quaker Oats and eggs. This composition was mixed well and placed into 3 cans
as described above for each coating being tested. After steam processing and cooling
overnight, the cans were opened and the cans inverted and shook up to five (5) times
to release the contents from the interior of the can. The results are reported below:
| Examples |
Evaluation |
| 1 |
Complete release |
| 2 |
Meat had to be pulled out with a fork |
| 3 |
Partial release with some residual meat clinging to coating surface |